OXYGEN SENSOR - checkdrive train

[terry10]

I have had the "check drive train" message appear several times -each time when towing, but the car sems to be travelling ok. I have pulled over and called the NRMA who tell me it is oxygen sensor. Have taken it back to the dealer who tells me they cannot find any wrong. I have read a little on the forum about the O2 sensor. My petrol consumption seems normal - 14l/100 while towing. Does the O2 sensor react to overheating. Any recommendations as to the best way to fix this. Is it the sensors or is it a fault in the management system?

[TimWalton]

Has the NRMA actually come and had a look at the car or did you just talk to them on the phone? My advice is: don't take what they say as gospel as I've had far too many cars come into work and they've been diagnosed incorrectly. Sorry to anyone who is actually part of the NRMA or has family in it but it's my opinion.

Now don't quote me on anything I'm about to say as I may have some things wrong. I'm only an apprentice mechanic but I'll try and help.

Anyway... O2 sensors generally don't react to overheating. Although, the fact that it comes on when you're towing might have something to do with it.

In a nutshell, O2 sensors analyse the exhaust gases and from that reading, tell the ECU what the ratio of air to fuel is and the ECU then adjusts fuel trims and a bunch of other things to make the engine work at its best.

However if the ECU gets a reading of a large imbalance of fuel to air and it can't adjust the trims accordingly, it will log a fault code and set off the engine warning light.

Wild guess here: it comes on when you're accelerating or going up hills? If so, then a lot of fuel is being dumped into the engine and there may not be enough airflow to balance it out, possibly from a clogged air filter or a dirty sensor giving a wrong reading. As a result, O2 sensor gets high reading of fuel and engine light comes on.

If it doesn't come on when driving around normally towing is what's setting it off.

[terry10]

Thanks for your reply and explanation Tim.
Yes NRMA have come each time with the gadget they connect and got an error message.

I usually drive the car fairly gently when not towing- due to fuel price -and dont have problems. Last time I got the "check drive train" was climbing and approaching a crest of hill and starting to slow as I knew they was a very big down hill on the other side. I annoys me because it always happens when I am away from home with my caravan.

[terry10]

Thanks for your reply and explanation Tim.
Yes NRMA have come each time with the gadget they connect and got an error message.

I usually drive the car fairly gently when not towing- due to fuel price -and dont have problems. Last time I got the "check drive train" was climbing and approaching a crest of hill and starting to slow as I knew they was a very big down hill on the other side. I annoys me because it always happens when I am away from home with my caravan.

[TimWalton]

Well I sound like a dick now for bagging out the NRMA and then agreeing with them...whoops. Oh well. Did they recommend any action to fix the problem or did they just tell you what it was?

When was the last time you had your air filter replaced? If it's really dirty then it might be part of the reason you're getting the light, as I mentioned in my previous post.

The silver lining thought is that it's unlikely your car will conk out when you're out and about with the van. I did say unlikely, but from what you've told me, I think I'm pretty close with my diagnosis. The best course of action is to take it to a mechanic and ask if there's anything they can do to fix it/prevent any future problems. At the best you're looking at an air filter (for your model commodore, around the twenty-something dollar mark) and worst, an O2 sensor ($40-$50 generally plus labour) so it's unlikely to be bank-breaking.

Hope this helps.

[terry10]

I will get them to check the air filter and the O2 sensors when I take it back to the dealer. One of the times it happened before they swapped the sensors around. Maybe time for a new sensor It had just had a service - and it has only done about 50000km so I am not sure whether the air filter has been changed . I am also thinking of fitting a transmission cooler but I assume thats not the problem just that I always think thats the problem when it get the "checkdrive train" message. I would be happier if it said check check fuel or exhaust system.

Thanks again for your comments

Terry

[RiCeY]

An O2 sensor code doesnt always mean the o2 sensor is faulting. It can mean the car is running lean or rich beyond predetermined limits.

It would help to know exactly what codes are being logged...